1. Field of the Invention
The present invention relates to image forming apparatus such as copiers and laser printers employing an electrophotographic system or electrostatic recording system and, more particularly, to configurations of an intermediate transfer module and a secondary transfer module.
2. Description of the Related Art
In general, conventional image forming apparatus such as copiers and laser printers employing an electrophotographic system or electrostatic recording system as described above have a configuration in which image exposure is performed on a surface of a photosensitive drum to form an electrostatic latent image; the electrostatic latent image formed on the surface of he photosensitive drum is developed by a developing device to form a toner image in a predetermined color, and the toner image is directly transferred on to and fixed on recording paper or temporarily transferred to an intermediate transfer body and is thereafter transferred on to the recording paper at a time to form an image.
When a color image is formed by an image forming apparatus as described above, as shown in FIG. 27, a configuration may be employed in which a latent image forming step of performing image exposure on a surface of a single photosensitive drum 200 with an image exposure device 201 to form an electrostatic latent image associated with a predetermined color and a developing step of developing the latent image with a developing device 202 for the associated color are repeated for a predetermined number of colors; toner images T having the predetermined colors sequentially formed on the surface of the photosensitive drum 200 are subjected to primary transfer on to an intermediate transfer belt 203 on a multiplex basis; and the toner images are subjected to secondary transfer from the intermediate transfer belt 203 on to recording paper 204 at a time to form a color image.
Image forming apparatus as described above include so-called tandem type image forming apparatus having plural (e.g., four) photosensitive drums each associated with a predetermined color and having a configuration in which toner images in predetermined colors sequentially formed on surfaces of the respective photosensitive drums are subjected to primary transfer on to an intermediate transfer belt on a multiplex basis; and the toner images are thereafter subjected to secondary transfer from the intermediate transfer belt on to recording paper at a time to form a color image.
For example, as shown in FIG. 29, a tandem type image forming apparatus as described above has four image forming units, i.e., a black image forming unit 300K for forming an image in black (K), a yellow image forming unit 300Y for forming an image in yellow (Y), a magenta image forming unit 300M for forming an image in magenta (M) and a cyan image forming unit 300C for forming an image in cyan (C). The four image forming units 300K, 300Y, 300M and 300C arc horizontally arranged at constant intervals from each other. Below the image forming units 300K, 300Y, 300M and 300C for black (K), yellow (Y), magenta (M) and cyan (C), an intermediate transfer belt 301 for transferring toner images sequentially formed by the respective image forming units in an overlapping relationship with each other is provided such that it is driven by plural rolls 311 through 314 including driving rolls for rotation in the direction indicated by the arrow. For example, the intermediate transfer belt 301 is configured in the form of an endless belt by forming a synthetic resin film made of polyimide or the like having flexibility in the form of a belt and by connecting both ends of the synthetic resin film formed in a belt-like configuration by means of welding or the like.
All of the image forming units 300K, 300Y, 300M and 300C for black (K), yellow (Y), magenta (M) and cyan (C) have the same configuration, and toner images in black (K), yellow (Y), magenta (M) and cyan (C) are sequentially formed by the respective four image forming units 300K, 300Y, 300M and 300C as described above. The image forming units 300K, 300Y, 300M and 300C for the respective colors have a photosensitive drum 302, and a surface of the photosensitive drum 302 is uniformly charged by a scorotron 303 for primary charging and is thereafter scanned and exposed by laser light for image formation from an image exposure device 304 in accordance with image information to form electrostatic latent images. The electrostatic latent images formed on the surface of the photosensitive drums 302 are developed into visible toner images by developing devices 305 of the respective image forming units 300K, 300Y, 300M and 300C with toners in respective colors, i.e., black, yellow, magenta and cyan, and the visible color images are transferred on to the intermediate transfer belt 301 by a transfer charger 306 in an overlapping relationship with each other. The toner images in black, yellow, magenta and cyan transferred on to the intermediate transfer belt 301 on a multiplex basis are transferred at a time on to transfer paper 307 by a secondary transfer roll 315 urged into contact with an opposite roll 314 and are thereafter subjected to a fixing process at a fixing device 308 to form a color image.
Reference numbers 309 and 310 in FIG. 29 represent a photosensitive body cleaner and an intermediate transfer belt cleaner, respectively.
However, the above-described related art has problems as described below. In an image forming apparatus having a configuration as described above, for example, when the intermediate transfer belt is pulled out from the body of the apparatus, the intermediate transfer belt must be spaced from the photosensitive drum. Most image forming apparatus as shown in FIG. 27 have a configuration in which an intermediate transfer belt 203 is spaced from a photosensitive drum 200 by pushing a surface of the intermediate transfer belt 203 with a push-down member 205 and by retracting a primary transfer roll 206 downward, as shown in FIG. 28. In this configuration, a secondary transfer roll 207 is also retracted downward.
In this case, however, since the push-down member 205 must be urged against a surface of the intermediate transfer belt 203, a problem arises in that the intermediate transfer belt 203 can be damaged. In the case of a tandem type image forming apparatus, since an intermediate transfer belt 301 is long and four photosensitive drums 302C, 302M, 302Y and 302K are in contact with the intermediate transfer belt 301 as shown in FIG. 30, it is very difficult to provide a configuration in which the intermediate transfer belt 301 is spaced from the four photosensitive drums 302C, 302M, 302Y and 302K by a push-down member.
In order to allow an intermediate transfer belt to be pulled out from the body of the apparatus while avoiding such problems, a configuration may be employed in which an intermediate transfer belt is held at two positions, i.e., a position where it transfers an image from a photosensitive drum and a position where it is spaced from the photosensitive drum and pulled out and in which a secondary transfer portion has two or more positions including a position where it transfers an image on to recording paper and a position where it is pulled out. When the intermediate transfer belt of such an image forming apparatus is pulled out from the body of the apparatus, the secondary transfer portion must be moved to the pull-out position and the intermediate transfer belt must be thereafter moved to the spaced pull-out portion.
However, the above-described configuration has a problem in that the intermediate transfer belt can be subjected to damage that reduces image quality and the apparatus can be broken in the worst case because the intermediate transfer belt and secondary transfer portion rub and scratch each other when the operation of moving the secondary transfer portion to the pull-out position and the operation of moving the intermediate transfer belt to the spaced pull-put position are carried out in a wrong order or when the intermediate transfer belt is moved to the spaced pull-out position without moving the secondary transfer portion.
Further, in the above-described configuration, a great operating force is required to move the intermediate transfer belt and the like and a mechanism for moving them becomes complicated when a moving handle for moving the intermediate transfer belt and secondary transfer portion is not located near the positions of the intermediate transfer belt and secondary transfer portion, which results in a problem in that the intermediate transfer belt and secondary transfer portion may not be properly positioned.
The present invention has been made to overcome the above problems and provides a so-called tandem type image forming apparatus having plural image carrying bodies and an intermediate transfer belt in which the intermediate transfer belt can be spaced from the image carrying bodies without causing any damage on the intermediate transfer belt.
The present invention also provides an image forming apparatus free from the possibility of damage and the like of the apparatus and an intermediate transfer belt even when it has a configuration in which an intermediate transfer belt is held at two positions, i.e., a position where it transfers an image from an image carrying body and a position where it is spaced from the image carrying body and pulled out and in which a secondary transfer portion has a position where it transfers an image on to a recording material and a position where it is pulled out.
The present invention also provides an image forming apparatus in which an operating force for moving the positions of an intermediate transfer belt and a secondary transfer portion can be reduced and in which a mechanism for moving the positions of the intermediate transfer belt and the secondary transfer portion can be simplified.
In order to solve the above problems, according to a first aspect of the invention, an image forming apparatus has a configuration in which there is provided plural image carrying bodies which form visible images using charged colorants in colors different from each other, a belt-shaped intermediate transfer body to which primary transfer of the visible images formed by the plural image carrying bodies is carried out and which circulates with the visible images formed of the charged colorant carried thereon, a secondary transfer member which transfers the visible images transferred onto the belt-shaped intermediate transfer belt to a recording material at a time, a belt module which supports the belt-shaped intermediate transfer body such that it can circulate and a secondary transfer module which supports the secondary transfer member such that it is urged into contact with or close to the belt-shaped intermediate transfer body supported by the belt module and a retracting unit which retracts the belt module along with the secondary transfer module such that the belt-shaped intermediate transfer body is spaced from all of the image carrying bodies.
According to a second aspect of the invention, an image forming apparatus according to the first aspect has a configuration including a first retracting unit which retracts the belt module such that the belt-shaped intermediate transfer body is spaced from all of the image carrying bodies and a second retracting unit which retracts the secondary transfer module such that a secondary transfer member is spaced from the position in contact with or close to the belt-shaped intermediate transfer body.
Further, according to a third aspect of the invention, an image forming apparatus according to the first or second aspect has a configuration including a first pull-out unit which pulls out the belt module from the body of the image forming apparatus and a second pull-out unit which pulls out the secondary transfer module from the body of the image forming apparatus.
Furthermore, according to a fourth aspect of the invention, an image forming apparatus according to the second or third aspect has a configuration in which the first retracting unit retracts the belt module such that the belt-shaped intermediate transfer body is spaced from all of the image carrying bodies after the secondary transfer module is retracted by the second retracting unit such that it is spaced from the belt-shaped intermediate transfer body.
Further, according to a fifth aspect of the invention, an image forming apparatus according to the fourth aspect has a configuration including an erroneous operation preventing unit which prevents the operation of the first retracting unit to retract the belt module such that the belt-shaped intermediate transfer body is spaced from all of the image carrying bodies before the secondary transfer module is retracted by the second retracting unit such tat it is spaced from the belt-shaped intermediate transfer body.
Further, according to a sixth aspect of the invention, in an image forming apparatus according to the fifth aspect, the erroneous operation preventing unit is configured to disable the operation of the firs retracting unit to retract the belt module such that the belt-shaped intermediate transfer body is spaced from all of the image carrying bodies unless the secondary transfer module is retracted by the second retracting unit such that it is spaced from the belt-shaped intermediate transfer body.
Furthermore, according to a seventh aspect of the invention, in an image forming apparatus according to the sixth aspect, the erroneous operation preventing unit is constituted by a part of a handle member of the first retracting unit which retracts the belt module such that the belt-shaped intermediate transfer body is spaced from all of the image carrying bodies and a part of the secondary transfer module,
Further, according to an eighth aspect of the invention, an image forming apparatus according to the seventh aspect has a configuration in which the handle member of the first retracting unit is provided in the vicinity of a positioning portion of the belt module.
Further, according to a ninth aspect of the invention, an image forming apparatus according to the seventh or eighth aspect has a configuration in which the handle member of the first retracting unit is normally covered by a protective cover which is not opened and closed by a user.
According to a tenth aspect of the invention, there is provided a configuration including plural image carrying bodies, a belt-shaped intermediate transfer body to which primary transfer of visible images formed by the plural image carrying bodies is carried out and which circulates with the visible images carried thereon, a belt module which supports the belt-shaped intermediate transfer body such that it can be circulate, a secondary transfer module which supports a secondary transfer member such that it is urged into contact with or close to the belt-shaped intermediate transfer body supported by the belt module, a backup roll facing the secondary transfer member with the belt interposed therebetween, which supports the intermediate transfer belt from a back side thereof, an insulated casing which can be attached to and detached from the belt module, which is open at least in a region thereof facing the intermediate transfer belt and which contains and supports the backup roll and a retracting unit which retracts the belt module along with the secondary transfer module such that the belt-shaped intermediate transfer body is spaced from all of the image carrying bodies.
According to an eleventh aspect of the invention, there is provided a configuration including an image carrying body on which a toner image according to image information is formed, an intermediate transfer belt to which primary transfer of the toner image from the image carrying body is carried out, a transfer member which performs secondary transfer of the toner image on to a recording sheet by sandwiching the recording sheet with the intermediate transfer belt and itself, a backup roll provided in a face-to-face relationship with the transfer member with the intermediate transfer belt interposed therebetween, which supports the intermediate transfer belt from a back side thereof and an insulated casing which is open at least in a region thereof facing the intermediate transfer belt and which contains and supports the backup toll.
Finally, according to a twelfth aspect of the invention, there is provided a configuration in which the insulated casing and the backup roll contained in and supported by the insulated casing can be simultaneously attached and detached in the axial direction.
According to the first aspect of the invention, there is provided a configuration including a retracting unit which retracts a belt module along with a secondary transfer module such that a belt-shaped intermediate transfer body is spaced from all of image carrying bodies. As a result, the belt-shaped intermediate transfer belt can be spaced from all of the image carrying bodies without any damage to the belt-shaped intermediate transfer body because the belt module can be retracted by the retracting unit such that the belt-shaped intermediate transfer body is spaced from all of the image carrying bodies.
According to the second aspect of the invention, there is provided a configuration including a first retracting unit which retracts the belt module such that the belt-shaped intermediate transfer body is spaced from all of the image carrying bodies and a second retracting unit which retracts the second transfer module such that a second transfer member is spaced from a position in contact with or close to the belt-shaped intermediate transfer body. As a result, the first retracting unit can prevent the secondary transfer module from hindering the belt module from spacing the belt-shaped intermediate transfer body from all of the image carrying bodies.
Further, according to the third aspect of the invention, there is provided a configuration including a first pull-out unit which pulls out the belt module from the body of the image forming apparatus and a second pull-out unit which pulls out the secondary transfer module from the body of the image forming apparatus. As a result, the possibility of damage or breakage of the belt-shaped intermediate transfer body can be eliminated even in a configuration in which the intermediate transfer belt is held at two positions, i.e., a position where it transfers images from the image carrying bodies and a position where it is spaced from the image carrying bodies and pulled out and in which the secondary transfer portion has a position where it transfers we images on to a recording material and a position where it is pulled out.
Furthermore, according to the fourth aspect of the invention, the first retracting unit retracts the belt module such that the belt-shaped intermediate transfer body is spaced from all of the image carrying bodies after the secondary transfer module is retracted by the second retracting unit such that it is spaced from the belt-shaped intermediate transfer body. As a result, the first retracting unit can prevent the secondary transfer module from hindering the belt module from spacing the belt-shaped intermediate transfer body from all of the image carrying bodies.
Further, according to the fifth aspect of the invention, there is provided a configuration including an erroneous operation preventing unit which prevents the operation of the first retracting unit to retract the belt module such that the belt-shaped intermediate transfer body is spaced from all of the image carrying bodies before the secondary transfer module is retracted by the second retracting unit such that it is spaced from the belt-shaped intermediate transfer body. As a result, the erroneous operation preventing unit can prevent the first retracting unit from erroneously retracting the belt module first, thereby preventing the belt module from striking against other members to cause damage thereon.
Further, according to the sixth aspect of the invention, there is provided a configuration in which the erroneous operation preventing unit disables the operation of the first retracting unit to retract the belt module such that the belt-shaped intermediate transfer body is spaced from all of the image carrying bodies unless the secondary transfer module is retracted by the second retracting unit such that it is spaced from the belt-shaped intermediate transfer body. As a result, the erroneous operation preventing unit can prevent the first retracting unit from erroneously retracting the belt module first, thereby preventing the belt module from striking against other members to cause damage thereon with improved reliability.
Furthermore, according to the seventh aspect of the invention, there is provided a configuration in which the erroneous operation preventing unit is constituted by a part of a handle member of the first retracting unit which retracts the belt module such that the belt-shaped intermediate transfer body is spaced from all of the image carrying bodies and a part of the secondary transfer module. It is therefore possible to more reliably prevent the belt module from striking against other members to cause damage thereon without a complicated configuration.
Further, according to the eighth aspect of the invention, there is provided a configuration in which the handle member of the first retracting unit is provided in the vicinity of a positioning portion of the belt module. It is therefore possible to reduce an operating force required to move the belt-shaped intermediate transfer body and secondary transfer portion.
Further, according to the ninth aspect of the invention, there is provided a configuration in which the handle member of the first retracting unit is normally covered by a protective cover which is not opened and closed by a user. It is possible to reliably prevent a user from erroneously operating the handle member of the first retracting unit.
According to the tenth, eleventh and twelfth aspects of the invention, since a backup roll is supported by a casing, the casing can be detachable using a rail which is not shown to be replaced easily even if it is worn as a result of rotation.